Some x pipes are built from solid pipe. They are just pipe with holes cut into them and welded back together. I have a BBK x pipe. The BBK pipe has a box (sort of like a prochamber) built out sheet metal that the pipe or welded into. The sheet metal makes the pipe have a loud, high pitched sound that you can hear really good from beside the car and inside the car. A friend of mine bought a x pipe that was just pipe fused together to make the x and it sounded just like an h pipe. The pitch is really loud at certain rpms. I have 40 series flows and at certain rpms the pitch from the x pipe drowns out the flows. The high pitch sound is made from the vibrations of the sheet metal.

 

so for a deeper sound with shorty header, and 40 flows on a 5.0 which would give it the smoothest and deepest and loudest sound.......o/r H or an O/R X

 

smooth and deep = catted H

deep and loud = O/R H